I calculate my fuel for a 4500nm with a B777-300 flight as follows:
4500nm/480knts = 9.375 hrs x 22,000lbs = 206,250lbs x 1.08 = 222,750lbs and depending on the airport I'll add taxi fuel according to EST. taxi time.
So I will use 222,300lbs + taxi fuel to complete a 4500nm trip.
The 22,000lbs is fuel consumption per engine per hr. (11,000 x 2).
The 1.08 is used as my reserve fuel, usually 45 min. worth. (16,500)
Are these calculations correct? I usually arrive at my destination with about 20,000lbs in the tank when landing.
I think that the fuel calculations given in FS are not realistic so I compute my own for each trip.
How do you calculate fuel and cruise level for your trips?